Different effects of bisoprolol on heart rate in patients with ischemic or idiopathic dilated cardiomyopathy (a 24-hour Holter substudy of the Cardiac Insufficiency Bisoprolol Study [CIBIS])

β-blockers in stage B: a precursor of heart failure

β-blockers are an important treatment of heart failure (HF) and are useful in reducing the progression of the syndrome. They should be considered for patients with asymptomatic left ventricular (LV) dysfunction. Evidence-based β-blocker therapy (bisoprolol, carvedilol, or metoprolol succinate) in combination with standard therapy is a mainstay of treatment of all symptomatic patients with LV systolic dysfunction. Patients in stage B also benefit from the early introduction of β-blockers, but there are no large randomized clinical trials to support this strategy. Whether there is a role for ivabradine in the treatment of HF is not clear.

Etiology-dependency of ionic remodeling in cardiomyopathic rabbits

BACKGROUND

Both dilated (DCM) and ischemic cardiomyopathy (ICM) are associated with action potential (AP) prolongation due to ionic remodeling. In humans, AP prolongation is more pronounced in myocytes isolated from explanted DCM than ICM hearts. However, there is a large variability due to confounding factors, including age, sex, concomitant disease, drug treatment, and progression of the disease at the time of heart transplantation. Here, we investigated the etiology-dependency of ionic remodeling in standardized rabbit models of ICM and DCM.

METHODS

ICM and DCM were induced by chronic infarction or combined volume and pressure overload, respectively. APs and membrane currents were measured using patch-clamp methodology.

RESULTS

Both ICM and DCM caused hypertrophy, but this hypertrophy was more prominent in DCM rabbits that also developed heart failure (DCM(F)), as revealed by the presence of ascites. Animals of either model showed AP prolongation. While the AP prolongation was similar by the same degree of hypertrophy, AP prolongation in DCM(F) was more pronounced. In all models, L-type Ca(2+) current, inward rectifier K(+) current, and rapid delayed rectifier K(+) current were unaltered, but the transient outward K(+) current (I(to 1)) density was significantly reduced. The I(to 1) decrease was not associated with differences in voltage-dependency of (in)activation. I(to 1) downregulation was similar in ICM and DCM with the same degree of hypertrophy, but was more pronounced in DCM(F).

CONCLUSIONS

The amount of ionic remodeling and AP prolongation in cardiomyopathic rabbits is due to differences in the amount of hypertrophy rather than differences in the etiology of the cardiomyopathy.

Pathophysiological characteristics of heart rate recovery in heart failure

PURPOSE

Heart failure (HF) is associated with blunted HR recovery after exercise. The determinants of altered HR recovery in HF are unknown. The aim of this study was to investigate clinical correlates of HR recovery in HF patients.

METHODS

Echocardiography, pulmonary function tests, exercise testing, and neurohormonal measurements were performed in 98 HF patients. HR recovery was calculated as the difference between heart rate at peak exercise and at 1 min into a recovery period. Study subjects were divided into three groups based on HR recovery tertiles: group 1 (HR recovery < or = 6 bpm), group 2 (7 < or = HR recovery < or = 12), and group 3 (HR recovery > or = 13).

RESULTS

There were significant differences between the groups in multiple parameters. Compared with group 3, patients in group 1 had greater E/A ratios (1.81 +/- 0.26 vs 0.98 +/- 0.12, P = 0.011), shorter deceleration time (170 +/- 11 vs 223 +/- 11 ms, P = 0.016), and higher plasma atrial natriuretic peptide levels (207 +/- 32 vs 101 +/- 12 pg.mL, P = 0.008), indicating higher left ventricular filling pressures and elevated left atrial pressures. Pulmonary function tests were suggestive of greater restrictive changes in the lungs. Finally, subjects in group 1 had impaired exercise capacity, as evidenced by shorter exercise duration (5.2 +/- 0.2 vs 8.3 +/- 0.4 min, P < 0.001), lower peak VO2 (14.6 +/- 0.6 vs 22.2 +/- 1.0 mL.kg(-1).min(-1), P < 0.001), higher VE/VCO2 ratios (36.4 +/- 1.1 vs 31.1 +/- 0.9, P = 0.001), and reduced chronotropic responses to exercise (39 +/- 3 vs 69 +/- 4 bpm, P < 0.001).

CONCLUSION

HR recovery may be a clinically useful index identifying HF patients with distinct echocardiographic, neurohormonal, and hemodynamic characteristics. This may have implications for our understanding of the pathophysiology of impaired HR recovery in HF as well as for the clinical evaluation of such patients.

[Prediction of intolerance to beta blocker therapy in chronic heart failure patients using BNP]

Beta-blocker therapy is actually recommended as first line therapy for systolic heart failure. However, beta-blocker have a low prescription rate comparatively to ACEI. Beta-blocker potential side effects as bradycardia, hypotension and especially acute decompensation could explain this under prescription. Clinical data could easily identify high-risk patients for hypotension or bradycardia but not high-risk patients for induced decompensation linked to beta-blocker therapy. BNP could identify these patients with a high sensitivity. Patients with BNP above 1000 pg/ml had a 40% risk of acute decompensation after introduction or increase of beta-blocker therapy. As a conclusion, clinicians must be very cautious for introducing or increasing Carvedilol therapy in patients with high BNP levels.

beta-Blockers in congestive heart failure

Recent advances in the understanding of the basic mechanisms underlying congestive heart failure (CHF) have focused on the role of neurohormonal activation. Chronic adrenergic overstimulation is directly toxic to myocardial cells, impairs function, causes peripheral vasoconstriction and may induce programmed cell death via apoptosis. beta-Adrenergic blockade can interrupt this pathological process. Accumulating evidence now points to a clear role for beta-blocking agents in the management of heart failure, reducing both the morbidity and mortality associated with CHF. This report will review the recent clinical trials supporting the use of beta-blockers in CHF, briefly highlight some practical considerations in the use of these drugs in patients with CHF and discuss several areas of controversy in which further study is needed.